Some of the posts remind me of a problem I'm having with a printer on which I've updated/upgraded the firmware. The first layer of your print should be examined for proper "squash" and I don't mean the vegetable (fruit?) in this context. You want to have a cross section of the filament to be more horizontal than circular. If you're getting anything close to circular, the first layer nozzle setting is far too high. Curious Aardvark references z-gap and that's the key aspect of your problem, I'll wager.